Wondering why your preg_replace fails, even if you have used preg_quote?Try adding the delimiter / - preg_quote($string, '/');
(PHP 4, PHP 5, PHP 7, PHP 8)
preg_quote — Quote regular expression characters
preg_quote() takes str
and puts a backslash in front of every character that is part of
the regular expression syntax. This is useful if you have a
run-time string that you need to match in some text and the
string may contain special regex characters.
The special regular expression characters are:
. \ + * ? [ ^ ] $ ( ) { } = ! < > | : - #
Note that / is not a special regular expression character.
Note:
Note that preg_quote() is not meant to be applied to the $replacement string(s) of preg_replace() etc.
strThe input string.
delimiter
If the optional delimiter is specified, it
will also be escaped. This is useful for escaping the delimiter
that is required by the PCRE functions. The / is the most commonly
used delimiter.
Returns the quoted (escaped) string.
| Version | Description |
|---|---|
| 7.3.0 |
The # character is now quoted
|
| 7.2.0 |
delimiter is nullable now.
|
Example #1 preg_quote() example
<?php
$keywords = '$40 for a g3/400';
$keywords = preg_quote($keywords, '/');
echo $keywords; // returns \$40 for a g3\/400
?>
Example #2 Italicizing a word within some text
<?php
// In this example, preg_quote($word) is used to keep the
// asterisks from having special meaning to the regular
// expression.
$textbody = "This book is *very* difficult to find.";
$word = "*very*";
$textbody = preg_replace ("/" . preg_quote($word, '/') . "/",
"<i>" . $word . "</i>",
$textbody);
?>Note: This function is binary-safe.
Wondering why your preg_replace fails, even if you have used preg_quote?Try adding the delimiter / - preg_quote($string, '/');To escape characters with special meaning, like: .-[]() and so on, use \Q and \E.For example:<?php echo ( preg_match('/^'.( $myvar = 'te.t' ).'$/i', 'test') ? 'match' : 'nomatch' ); ?>Will result in: matchBut:<?php echo ( preg_match('/^\Q'.( $myvar = 'te.t' ).'\E$/i', 'test') ? 'match' : 'nomatch' ); ?>Will result in: nomatchIt should be noted that the forward slash is not escaped. Since many regexes are surrounded by forward slashes, if you have one in your regex as text you must escape it yourself otherwise it'll terminat the regex.List of specials is incomplete:--- sample code ---$specials = '.\+*?[^]$(){}=!<>|:-';for ($i = 0; $i <= 255; $i++) { if (chr($i) !== preg_quote(chr($i))) { printf("Character 0x%02x quoted%s\n", $i, (strpos($specials, chr($i)) === FALSE) ? ' (+)' : ''); } /* if */} /* for */--- sample code ------ output ---Character 0x00 quoted (+)Character 0x21 quotedCharacter 0x24 quotedCharacter 0x28 quotedCharacter 0x29 quotedCharacter 0x2a quotedCharacter 0x2b quotedCharacter 0x2d quotedCharacter 0x2e quotedCharacter 0x3a quotedCharacter 0x3c quotedCharacter 0x3d quotedCharacter 0x3e quotedCharacter 0x3f quotedCharacter 0x5b quotedCharacter 0x5c quotedCharacter 0x5d quotedCharacter 0x5e quotedCharacter 0x7b quotedCharacter 0x7c quotedCharacter 0x7d quoted--- output ---I discovered that, in addition to escaping the special regular expression characters, preg_quote() encodes the NUL byte to its octal representation:<?phpvar_dump(preg_quote("\0"));?>Output:string(4) "\000"To have a higher level control of what your pattern looks like, try T-Regx:Pattern::inject('This is (my|our) pattern: @', [$_GET['name']]);