PHP Reguliere Expressie Functies
PHP Reguliere Expressie Introductie
Met reguliere expressies kunt u patronen in strings zoeken en vervangen.
Installatie
De reguliere expressiefuncties van PHP maken deel uit van de PHP-kern. Er is geen installatie vereist om deze functies te gebruiken.
Runtime-configuratie
Deze instellingen in php.ini kunnen worden gebruikt om de hoeveelheid tijd of middelen te beperken die worden gebruikt bij het evalueren van reguliere expressies.
| Name | Default | Description | Changeable |
|---|---|---|---|
| pcre.backtrack_limit | "1000000" | The maximum number of backtracks that the regular expression engine is allowed to do while evaluating an expression. (available since PHP 5.2) | PHP_INI_ALL |
| pcre.recursion_limit | "100000" | The maximum recursion depth that the regular expression engine is permitted to reach while evaluating an expression. (available since PHP 5.2) | PHP_INI_ALL |
| pcre.jit | "1" | When set to "1" this enables PCRE's (Perl-Compatible Regular Expressions) just-in-time compilation. (available since PHP 7.0) | PHP_INI_ALL |
PHP Reguliere Expressie Functies
| Function | Description |
|---|---|
| preg_filter() | Returns a string or an array with pattern matches replaced, but only if matches were found |
| preg_grep() | Returns an array consisting only of elements from the input array which matched the pattern |
| preg_last_error() | Returns an error code indicating the reason that the most recent regular expression call failed |
| preg_match() | Finds the first match of a pattern in a string |
| preg_match_all() | Finds all matches of a pattern in a string |
| preg_replace() | Returns a string where matches of a pattern (or an array of patterns) are replaced with a substring (or an array of substrings) in a given string |
| preg_replace_callback() | Given an expression and a callback, returns a string where all matches of the expression are replaced with the substring returned by the callback |
| preg_replace_callback_array() | Given an array associating expressions with callbacks, returns a string where all matches of each expression are replaced with the substring returned by the callback |
| preg_split() | Breaks a string into an array using matches of a regular expression as separators |
| preg_quote() | Escapes characters that have a special meaning in regular expressions by putting a backslash in front of them |
Modifiers voor reguliere expressies
Modifiers kunnen wijzigen hoe een zoekopdracht wordt uitgevoerd.
| Modifier | Description |
|---|---|
| i | Performs a case-insensitive search |
| m | Performs a multiline search (patterns that search for the beginning or end of a string will match the beginning or end of each line) |
| u | Enables correct matching of UTF-8 encoded patterns |
Reguliere expressiepatronen
Haakjes worden gebruikt om een reeks tekens te vinden:
| Expression | Description |
|---|---|
| [abc] | Find one character from the options between the brackets |
| [^abc] | Find any character NOT between the brackets |
| [0-9] | Find one character from the range 0 to 9 |
metakarakters
Metatekens zijn tekens met een speciale betekenis:
| Metacharacter | Description |
|---|---|
| | | Find a match for any one of the patterns separated by | as in: cat|dog|fish |
| . | Find just one instance of any character |
| ^ | Finds a match as the beginning of a string as in: ^Hello |
| $ | Finds a match at the end of the string as in: World$ |
| \d | Find a digit |
| \s | Find a whitespace character |
| \b | Find a match at the beginning of a word like this: \bWORD, or at the end of a word like this: WORD\b |
| \uxxxx | Find the Unicode character specified by the hexadecimal number xxxx |
Kwantificatoren
Kwantificatoren definiëren hoeveelheden:
| Quantifier | Description |
|---|---|
| n+ | Matches any string that contains at least one n |
| n* | Matches any string that contains zero or more occurrences of n |
| n? | Matches any string that contains zero or one occurrences of n |
| n{x} | Matches any string that contains a sequence of X n's |
| n{x,y} | Matches any string that contains a sequence of X to Y n's |
| n{x,} | Matches any string that contains a sequence of at least X n's |
Opmerking: als uw uitdrukking moet zoeken naar een van de speciale tekens, kunt u een backslash ( \ ) gebruiken om eraan te ontsnappen. Als u bijvoorbeeld naar een of meer vraagtekens wilt zoeken, kunt u de volgende uitdrukking gebruiken: $pattern = '/\?+/';