Multilingual Regular Expression Syntax (Pattern) in Php are an implementation of Perl (PCRE) with the PCRE library (See library).
Therefore, the syntax for patterns used in these functions closely resembles to Perl (PCRE) but not totally. See Perl Differences
The pattern must be enclosed by delimiters.
DelimiterPatternDelimiter[Modifiers]
where:
A delimiter:
If the delimiter character has to be used in the expression itself, it needs to be escaped by backslash.
Bracket (), {}, [] and <> must be escaped when they are used as literal characters.
The preg-quote function can be used to pre-escape a string pattern with a specified delimiter:
Example:
$keywords = '$40 for a g3/400';
$keywords = preg_quote($keywords, '/'); // The delimiter is a forward slash
echo $keywords; // returns \$40 for a g3\/400 // The dollar and / characters were quoted
The pattern modifiers are the regular expression flags and are located after the ending delimiter.
Example of case-insensitive matching:
#[a-z]#i
List:
From the doc: dirname, detection of the file system root.
dirname('.'); // Will return '.'.
dirname('/'); // Will return `\` on Windows and '/' on *nix systems.
dirname('\\'); // Will return `\` on Windows and '.' on *nix systems.
dirname('C:\\'); // Will return 'C:\' on Windows and '.' on *nix systems.
The pattern is then
$isRoot = preg_match("/(^\.|\\\\|[a-z]:\\\\)$/i", $path)
/foo bar/
#^[^0-9]$#
+php+
%[a-zA-Z0-9_-]%
(this [is] a (pattern))
{this [is] a (pattern)}
[this [is] a (pattern)]
<this [is] a (pattern)>
/<\/\w+>/
|(\d{3})-\d+|Sm
/^(?i)php[34]/
{^\s+(\s+)?$}
/href='(.*)' // missing ending delimiter
/\w+\s*\w+/J // unknown modifier 'J'
1-\d3-\d3-\d4| // missing starting delimiter
See book.pcre
Example:
$pattern = "carbon|eva";
if (preg_match("/$pattern/i",$pathString) === 1){
echo "We have a match";
}
By default, this extension is compiled using the bundled PCRE library. Alternatively, an external PCRE library can be used by passing in the –with-pcre-regex=DIR configuration option where DIR is the location of PCRE's include and library files.
escape character = backslash \
Example: Separate an HTML page with the p element node '</p>'
$localCount = count(preg_split("/<\/p>/",$section['content']));