PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Introducing Regular Expressions
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This function replaces all the instances of needle in haystack with new_needle and
returns the new version of the haystack.The optional fourth parameter, count, contains
the number of replacements made.
Note
You can pass all parameters as arrays, and the str_replace() function works remarkably intelligently.
You can pass an array of words to be replaced, an array of words to replace them with (respectively), and an
array of strings to apply these rules to. The function then returns an array of revised strings.
For example, because people can use the Smart Form to complain, they might use some
colorful words. As a programmer, you can easily prevent Bob’s various departments from
being abused in that way if you have an array $offcolor that contains a number of
offensive words. Here is an example using str_replace() with an array:
$feedback = str_replace($offcolor, ‘%!@*’, $feedback);
The function substr_replace() finds and replaces a particular substring of a string
based on its position. It has the following prototype:
string substr_replace(string string, string replacement,
int start, int [length] );
This function replaces part of the string string with the string replacement.Which
part is replaced depends on the values of the start and optional length parameters.
The start value represents an offset into the string where replacement should begin.
If it is zero or positive, it is an offset from the beginning of the string; if it is negative, it
is an offset from the end of the string. For example, this line of code replaces the last
character in $test with “X”:
$test = substr_replace($test, ‘X’, -1);
The length value is optional and represents the point at which PHP will stop replacing.
If you don’t supply this value, the string will be replaced from start to the end of the
string.
If length is zero, the replacement string will actually be inserted into the string without
overwriting the existing string. A positive length represents the number of characters
that you want replaced with the new string; a negative length represents the point
at which you would like to stop replacing characters, counted from the end of the string.
Introducing Regular Expressions
PHP supports two styles of regular expression syntax: POSIX and Perl. Both types are
compiled into PHP by default, and as of PHP versions 5.3 the Perl (PCRE) type cannot