Programming PHP

Table 4-4. Single-character escapes recognized by addcslashes( ) and stripcslashes( ) (continued)
ASCII value Encoding
10 \n
11 \v
12 \f
13 \r
Call addcslashes( ) with two arguments—the string to encode and the characters to
escape:
$escaped = addcslashes(string, charset);
Specify a range of characters to escape with the ".." construct:
echo addcslashes("hello\tworld\n", "\x00..\x1fz..\xff");
hello\tworld\n
Beware of specifying '0', 'a', 'b', 'f', 'n', 'r', 't', or'v' in the character set, as
they will be turned into '\0', '\a', etc. These escapes are recognized by C and PHP
and may cause confusion.
stripcslashes( ) takes a string and returns a copy with the escapes expanded:
$string = stripcslashes(escaped);
For example:
$string = stripcslashes('hello\tworld\n');
// $string is "hello\tworld\n"
Comparing Strings
PHP has two operators and six functions for comparing strings to each other.
Exact Comparisons
You can compare two strings for equality with the == and === operators. These operators
differ in how they deal with non-string operands. The == operator casts nonstring
operands to strings, so it reports that 3 and "3" are equal. The === operator
does not cast, and returns false if the types of the arguments differ.
$o1 = 3;
$o2 = "3";
if ($o1 == $o2) {
echo("== returns true");
}
if ($o1 === $o2) {
echo("=== returns true");
}
== returns true
86 | Chapter 4: Strings
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