php preg_replace remove number started string and execption

Question

I have three situations, where I need to remove numbers characters.

STRING200, after preg_replace I expect STRING
STRING 100 TEST, after preg_replace I expect STRING 100 TEST
STRING 400, after preg_replace I expect STRING 400

I have tested the following combinations using preg_replace in PHP

/^(?:[0-9]+\s)*/
/[0-9]*$/
/^[a-zA-Z]+[0-9]*$

But without success, does anyone have any suggestions?

before/after 'string 100 test' and 'string 400' are the same. — user557597
– user557597, Commented Jul 21, 2017 at 17:44

Wiktor Stribiżew · Accepted Answer · 2017-07-21 17:46:05Z

1

You may match 1+ digits after a letter until a word boundary and remove them:

preg_replace('~[a-zA-Z]\K\d+\b~', '', $s)

See the regex demo.

Or if you need to match the whole string (see another demo):

preg_replace('~^[a-zA-Z]+\K\d+$~', '', $s)

Pattern details:

[a-zA-Z] - an ASCII letter
\K - match reset operator omitting the matched letter from the match value
\d+\b - 1 or more digits followed by the end of word boundary.

NOTE: If the match is expected at the end of the string, replace \b with $ (end of string anchor).

A PHP test:

$arr = ['STRING200','STRING 100 TEST','STRING 400'];
foreach ($arr as $s) {
   echo preg_replace('~[a-zA-Z]\K\d+\b~', '', $s) . PHP_EOL;    
}
// => [ STRING, STRING 100 TEST, STRING 400 ]

edited Jul 21, 2017 at 17:46

answered Jul 21, 2017 at 17:40

Wiktor Stribiżew

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