Programming PHP

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symbol table entries for $worker and $other has a reference count of 2. * In other words, that memory can be reached two ways: through $worker or $other. But after $worker[1] is changed, PHP creates a new array for $worker, and the reference count of each of the arrays is only 1. When a variable goes out of scope (as a function parameter or local variable does at the end of a function), the reference count of its value is decreased by one. When a variable is assigned a value in a different area of memory, the reference count of the old value is decreased by one. When the reference count of a value reaches 0, its memory is freed. This is reference counting. Reference counting is the preferred way to manage memory. Keep variables local to functions, pass in values that the functions need to work on, and let reference counting take care of freeing memory when it’s no longer needed. If you do insist on trying to get a little more information or control over freeing a variable’s value, use the isset( ) and unset( ) functions. To see if a variable has been set to something, even the empty string, use isset( ): $s1 = isset($name); // $s1 is false $name = "Fred"; $s2 = isset($name); // $s2 is true Use unset( ) to remove a variable’s value: $name = "Fred"; unset($name); // $name is NULL Expressions and Operators An expression is a bit of PHP that can be evaluated to produce a value. The simplest expressions are literal values and variables. A literal value evaluates to itself, while a variable evaluates to the value stored in the variable. More complex expressions can be formed using simple expressions and operators. An operator takes some values (the operands) and does something (for instance, adds them together). Operators are written as punctuation symbols—for instance, the + and – familiar to us from math. Some operators modify their operands, while most do not. Table 2-3 summarizes the operators in PHP, many of which were borrowed from C and Perl. The column labeled “P” gives the operator’s precedence; the operators are listed in precedence order, from highest to lowest. The column labeled “A” gives the operator’s associativity, which can be L (left-to-right), R (right-to-left), or N (nonassociative). * It is actually 3 if you are looking at the reference count from the C API, but for the purposes of this explanation and from a user-space perspective, it is easier to think of it as 2. 34 | Chapter 2: Language Basics This is the Title of the Book, eMatter Edition Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved.
Table 2-3. PHP operators P A Operator Operation 19 N new Create new object 18 R [ Array subscript 17 R ! Logical NOT R ~ Bitwise NOT R ++ Increment R -- Decrement R (int), (double), (string), (array), (object) Cast R @ Inhibit errors 16 L * Multiplication L / Division L % Modulus 15 L + Addition L - Subtraction L . String concatenation 14 L > Bitwise shift right 13 N = Greater than, greater than or equal 12 N == Value equality N !=, Inequality N === Type and value equality N !== Type and value inequality 11 L & Bitwise AND 10 L ^ Bitwise XOR 9 L | Bitwise OR 8 L && Logical AND 7 L || Logical OR 6 L ?: Conditional operator 5 L = Assignment L +=, -=, *=, /=, .=, %=, &=, |=, ^=, ~=, = Assignment with operation 4 L and Logical AND 3 L xor Logical XOR 2 L or Logical OR 1 L , List separator This is the Title of the Book, eMatter Edition Copyright © 2002 O’Reilly & Associates, Inc. All rights reserved. Expressions and Operators | 35
Page 2 and 3: Programming PHP
Page 4 and 5: Programming PHP by Rasmus Lerdorf a
Page 6 and 7: Colophon Our look is the result of
Page 8 and 9: Accessing Individual Characters 79
Page 10 and 11: Concealing PHP Libraries 293 PHP Co
Page 12 and 13: clarify the explanations, and the p
Page 14 and 15: There is a web page for this book,
Page 17 and 18: Chapter 2 CHAPTER 2 Language Basics
Page 19 and 20: Comments Comments give information
Page 21 and 22: */ echo("l=$l m=$m n=$n\n"); ?> Now
Page 23 and 24: change. Constants are referred to b
Page 25 and 26: PHP recognizes floating-point numbe
Page 27 and 28: • The empty string ("") and the s
Page 29 and 30: Chapter 6 describes classes and obj
Page 31 and 32: The old value of $black is lost. In
Page 33: update_counter( ); update_counter(
Page 37 and 38: The division and multiplication ope
Page 39 and 40: Autoincrement and Autodecrement Ope
Page 41 and 42: Bitwise Operators The bitwise opera
Page 43 and 44: something is true. For example, you
Page 45 and 46: Because all operators are required
Page 47 and 48: if The if statement checks the trut
Page 49 and 50: A switch statement is given an expr
Page 51 and 52: if ($i == 5) break; // breaks out o
Page 53 and 54: This program adds the numbers from
Page 55 and 56: loops, and complain if the file bei
Page 57 and 58: XML Style Because of the advent of
Page 59 and 60: and other such niceties. Some will
Page 61 and 62: Chapter 3 CHAPTER 3 Functions A fun
Page 63 and 64: Typically, functions return some va
Page 65 and 66: As we discussed in Chapter 2, the e
Page 67 and 68: Example 3-5. Doubler redux function
Page 69 and 70: Missing Parameters PHP lets you be
Page 71 and 72: Anonymous Functions Some PHP functi
Page 73 and 74: echo "$who was $where"; Kilroy was
Page 75 and 76: As a special case, you can put a se
Page 77 and 78: • A padding specifier denoting th
Page 79 and 80: Boolean values and NULL are not mea
Page 81 and 82: Changing Case PHP has several funct
Page 83 and 84: The quote_style and charset argumen
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Query-string encoding The urlencode
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The comparison operators (=) also w
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The Levenshtein algorithm calculate
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The str_repeat( ) function takes a
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print_r($a);Array ( [0] => Fred [1]
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The c in strcspn( ) stands for comp
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These three kinds of patterns can b
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Subpatterns You can use parentheses
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Table 4-8. POSIX anchors Anchor Mat
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Example 4-1. Credit-card validator
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Character Classes Perl-style regula
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Trailing Options Perl-style regular
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A simple use of positive lookahead
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For example: preg_match('/y.*e$/',
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Pass an array of strings as subject
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Quoting for regular expressions The
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Identifying Elements of an Array Yo
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array is almost always a programmer
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Two or more consecutive commas in t
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echo "true!\n"; } if (array_key_exi
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EXTR_PREFIX_SAME, which says that t
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echo "$key is $value\n"; } 0 is spa
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The default argument, if provided,
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you need to answer questions like
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Example 5-3. Sorting arrays (contin
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Here’s how to randomize the order
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Sets Arrays let you implement the b
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Here’s the output from Example 5-
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Terminology Everyobject-oriented la
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You can use variable variables with
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} function set_name ($new_name) { $
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The object created bythe Person con
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Example 6-1. Displaying all declare
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Example 6-2. Object introspection f
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Here are some sample classes and ob
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PHP has two hooks for objects durin
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Example 6-5 shows the file next.php
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the request contains a blank line,
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SERVER_NAME The hostname, DNS alias
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The biggest difference between GET
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Figure 7-1. The chunkify form and i
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Example 7-4. Temperature conversion
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Example 7-6. Multiple selection val
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Example 7-8. Sticky multivalued che
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Files are stored in the server’s
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“me@aol” by requiring an at sig
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To mark a document as already expir
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A third technique for maintaining s
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Example 7-10. Preference selection
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Session basics To enable sessions f
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Custom storage By default, PHP stor
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When a session is completed, the de
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Chapter 8 CHAPTER 8 Databases PHP h
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columns, each of which has a name a
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Figure 8-1. The movie page the data
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$db = DB::connect($datasource); if
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string(4) "1962" ["name"]=> string(
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The executeMultiple( ) method takes
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echo "$k"; if (is_array($v)) { a_to
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Two HTML forms are needed to popula
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Example 8-3. Database connection ab
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Example 8-4. Backend administration
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Example 8-5. Adding a business (con
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Example 8-5. Adding a business (con
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The business listings page is illus
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The series of requests sent by the
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many colors as you need. The latter
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image-generating function. Example
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Example 9-4. Adding text to an imag
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Example 9-6. Displaying vertical Tr
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Example 9-8. Caching dynamic button
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You can also take this a step furth
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For a signed integer, the leftmost
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True Color Color Indexes The color
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Chapter 10 CHAPTER 10 PDF Adobe’s
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Figure 10-1. Hello world in a PDF d
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Type, Content-Disposition, and Cont
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Example 10-3. Changing the origin (
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Example 10-4. Text alignment within
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Example 10-5. Changing text attribu
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usr/share/fonts FontAFM LuciduxSans
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Adding an image to a PDF document i
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Example 10-8. Nonproportional scali
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Figure 10-9. A sample path The pdf_
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The width and height parameters spe
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Example 10-11. Using a template Th
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Example 10-12. Using bookmarks and
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Example 10-13. Specifying a link (c
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Figure 10-16. Closed note The conte
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In HTML, you often have an open tag
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Example 11-1. Generating an XML doc
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The end element handler is called w
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If your external entity reference h
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characters outside the target encod
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XML_ERROR_BAD_CHAR_REF XML_ERROR_BI
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Figure 11-2. Book details comment).
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Example 11-10. bookparse.xml (conti
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Example 11-12. News XSL transform
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more information). The xmlrpc exten
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equest, but it doesn’t know how t
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Chapter 12 CHAPTER 12 Security PHP
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These directives ensure that PHP er
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Restrict Filesystem Access to a Spe
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function or PHP’s copy( ) functio
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• Any system call (through functi
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You can globally disable particular
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Chapter 13 CHAPTER 13 Application T
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user.template. It uses the {DESTINA
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{ARTICLE} might be useful, as it wo
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} ob_start('rewrite'); ?> Visit our
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To turn off error reporting entirel
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Example 13-5. Log-rolling error han
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Before you begin optimization, ask
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changes you make to your code as yo
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• Only include or require files t
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MySQL replication Sometimes the dat
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Chapter 14 CHAPTER 14 Extending PHP
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examples, and you are strongly enco
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int Integer/long long Same as int a
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zend_module_entry rot13_module_entr
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for(i=0, ch=arg; i= 'A')&&(*ch
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if (extension_loaded($module)) { $s
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SWF_DIR=$i AC_MSG_RESULT(found in $
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If you compile the Apache module ve
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For example: zval **old, *new; *new
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The value returned from a PHP funct
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A More Complex Example Here’s an
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Table 14-4. RETURN-related convenie
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* ... */ }; PHP_MINIT_FUNCTION(foo)
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using SEPARATE_ZVAL( ), initializes
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The struct looks like this in the p
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zend_hash_update(&EG(symbol_table),
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Resources A resource is a generic d
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Chapter 15 CHAPTER 15 PHP on Window
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3. Windows 95/98/Me: the Windows sy
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Then explicitly load the module wit
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un under IIS, you will need to reim
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External Commands PHP uses the defa
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This creates a reference (VT_BYREF)
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Figure 15-3. Gleaning syntax from W
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Now we can complete the invoice wit
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multiple Workbooks, each of which c
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Example 15-4. Querying Excel via OD
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• Applications that want to use t
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Example 15-5. Add new phone number,
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Files, directories, and filesystem
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addcslashes string addcslashes(stri
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array_merge array array_merge(array
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array_search mixed array_search(mix
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asort void asort(array array[, int
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call_user_func mixed call_user_func
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chown bool chown(string path, mixed
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cos double cos(double value) Return
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Any characters in the format string
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each array each(array array) Create
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Any number of these options can be
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fflush int fflush(int handle) Commi
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filemtime int filemtime(string path
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If include is specified and is true
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ftell int ftell(int handle) Returns
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get_current_user string get_current
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get_parent_class string get_parent_
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getmypid int getmypid( ) Returns th
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header void header(string header[,
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implode string implode(array string
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is_double bool is_double(mixed valu
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is_scalar bool is_scalar(mixed valu
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Calculates the Levenshtein distance
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log double log(double number) Retur
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mkdir int mkdir(string path, int mo
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number_format string number_format(
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openlog int openlog(string identity
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parse_url array parse_url(string ur
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phpinfo void phpinfo([int what]) Ou
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printf int printf(string format[, m
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eaddir string readdir(int handle) R
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ound double round(double number[, i
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setlocale string setlocale(mixed ca
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sort void sort(array array[, int fl
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str_pad string str_pad(string strin
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%H Hour in 24-hour format, includin
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strncmp int strncmp(string one, str
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strtr string strtr(string string, s
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tmpfile int tmpfile( ) Creates a te
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unregister_tick_function void unreg
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wordwrap string wordwrap(string str
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old versions of aspell, you should
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DBM For very simple database instal
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Hyperwave Hyperwave is a database f
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mcrypt This extension provides an i
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pdflib pdflib provides support for
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Sybase This extension provides supp
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Symbols & (ampersand) &= (bitwise A
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| (vertical bar) |= (bitwise OR ass
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aspell PHP library, 457 assert() fu
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checksums mhash library, 464 valida
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cryptography mcrypt extension, 464
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DTD (Document Type Definition), 263
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System V Semaphores and Shared memo
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calling, 61 for each array element,
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H hash mark (#) in comments, 19 hea
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interlacing GIF images, 246 interna
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masks, using in string searches, 94
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serialization of, 153-157, 438 _ _s
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pdf_open_file() function, 234 pdf_p
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with echo, 76 with print() function
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S Sablotron C library (XSLT support
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sql_regcase() function, 443 sqrt()
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tan() function, 451 target encoding
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function parameters, 33 functions f
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xml_set_unparsed_entity_decl_handle
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