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This article mainly introduces the relevant knowledge of "how php detects whether there are only letters in a string". The editor shows you the operation process through an actual case. The method of operation is simple, fast and practical. I hope this article "how to detect whether there are only letters in a string by php" can help you solve the problem.

In php, the preg_match () function can be used with the regular expression "/ ^ [a-zA-Z\ s] + $/" to detect whether the string has only letters, the syntax "preg_match (" / ^ [a-zA-Z\ s] + $/ ", string)"; if the return value is 1, there are only letters, and if 0 is returned, it contains other characters.

Operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Php detects whether a string contains only letters. In other words, it determines whether a string is a pure English letter.

In php, you can use the preg_match () function with regular expressions to check.

Regular expression used: "/ ^ [a-zA-Z\ s] + $/"

The preg_match () function can search and match strings based on regular expressions. The syntax format of the function is as follows:

Preg_match ($pattern,$subject [, & $matches [, $flags = 0 [, $offset = 0])

The parameters are described as follows:

$pattern: the pattern to search for, that is, the edited regular expression

$subject: string to search for

$matches: optional parameter (array type), which will be populated with search results if $matches is provided. $matches [0] contains the text to which the full pattern matches, $matches [1] contains the text matched by the first capture subgroup, and so on

$flags: optional parameter. $flags can be set to PREG_OFFSET_CAPTURE. If this flag is passed, the string offset (relative to the target string) will be appended to the return for each occurrence of the match.

$offset: optional parameter that specifies where to start the search (in bytes) in the target string.

The preg_match () function can return the number of matches for $pattern, and its value will be 0 (mismatch) or 1, because preg_match () will stop searching after the first match.

If the return value is 1, there are only letters, and a return value of 0 contains other characters.

Example:

This kind of output is not very good. Let's customize a function and do a processing. Only letters will return true, otherwise false will be returned.

Function is_english ($str) {if (preg_match ("/ ^ [a-zA-Z\ s] + $/", $str)) {return true;} return false;}

Call the function to determine whether the string is made up of pure English letters

Var_dump (is_english ('php.cn')); / / bool (false) contains punctuation marks so returns false var_dump (is_english (' phpcn')); / / bool (true) var_dump (is_english ('phpcn123')); / / bool (false) contains 123var_dump (is_english (' Welcome here')); / / bool (false) is all in Chinese

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