وظائف التعبير العادي في PHP
مقدمة عن تعبير PHP العادي
تسمح لك التعبيرات العادية بالبحث عن أنماط في السلاسل واستبدالها.
التركيب
تعد وظائف التعبير العادي في PHP جزءًا من نواة PHP. لا يلزم التثبيت لاستخدام هذه الوظائف.
تكوين وقت التشغيل
يمكن استخدام هذه الإعدادات في php.ini لتحديد مقدار الوقت أو الموارد المستخدمة عند تقييم التعبيرات العادية.
| 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 |
وظائف التعبير العادي في PHP
| 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 |
معدِّلات التعبير العادي
يمكن أن تغير المعدلات كيفية إجراء البحث.
| 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 |
أنماط التعبير العادي
تستخدم الأقواس للبحث عن مجموعة من الأحرف:
| 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 |
الحروف الأولية
الحروف الأولية هي أحرف لها معنى خاص:
| 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 |
محددو الكمية
محددات الكميات تحدد الكميات:
| 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 |
ملاحظة: إذا احتاج تعبيرك إلى البحث عن أحد الأحرف الخاصة ، يمكنك استخدام شرطة مائلة للخلف (\) للتخلص منها. على سبيل المثال ، للبحث عن علامة استفهام واحدة أو أكثر ، يمكنك استخدام التعبير التالي: $ pattern = '/ \؟ + /'؛