How to keep only letters in php string

Implementation steps: 1. Use the preg_match_all() function with regular expressions to filter strings and retain only English letters. The syntax is "preg_match_all("/[a-zA-Z]/u","$str ",$arr);", the letters will be stored in the "$arr" array; 2. Use the implode() function to splice the result value into a new string, the syntax is "implode($arr[0])".

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

In PHP, you can use the preg_match_all() function and implode() function to make the string contain only letters.

Implementation steps:

Step 1: Use the preg_match_all() function with regular expressions to filter strings and only retain English letters

The preg_match_all() function matches all occurrences of the pattern in the string.

preg_match_all (pattern , subject ,matches,flags,offset);

• pattern:: The pattern to be searched, in string form.

• subject: Input string.

• matches: multi-dimensional array, output all matching results as output parameters, array sorting is specified by flags.

• #flags: Array result sorting, can be used in combination with the following flags

• offset: Usually, search starts from the beginning of the target string position starts. (Unit is bytes)
  

As you can see, the result is a two-dimensional array.

The required English letters are in the internal sub-array$arr[0], just convert it into a string.

Step 2: Use the implode() function to splice the result value into a string

The implode() function can convert a one-dimensional array into a string. The syntax is as follows:

implode($glue,$arr)

##Parameter Description Optional. Used to set a string, indicating that $glue is used to connect each element of the array together. By default, $glue is an empty string. Required. Arrays to be combined into strings.

$glue
$arr

#implode() function returns a string composed of array elements and the "$glue" character.

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