php regular expression not matching correctly

Question

This is a simplified example, but when I run this code the first does not match as it should. It only matches the first part and nothing else. The other two occurrences match properly so I have no idea why the first wouldn't.

$str = 'What is 5 plus three?What is 4 plus three?What is 4 plus two?';

$replacees = [
'/What is (.*?) plus two\?/',
'/What is (.*?) plus three\?/',
];
$replacers = [
'I know $1 and 2.',
'I know $1 and 3.',
];

print_r( preg_replace($replacees, $replacers, $str) );

The results from that are:

I know 5 plus three?I know 4 and 3.What is 4 and 2.

But I'm expecting:

I know 5 and 3.I know 4 and 3.I know 4 and 2.

The regex engine works from left to the right. Since the first "What is" matches, .*? will match all the string until "plus two?". — Casimir et Hippolyte
– Casimir et Hippolyte, Commented Dec 21, 2015 at 9:27
@HalayemAnis No, this is just a simple example to isolate the issue. — Robbie
– Robbie, Commented Dec 21, 2015 at 9:37

Sandeep J Patel · Accepted Answer · 2015-12-21 09:53:16Z

2

Hi All what you did was correct just flip the code as I have shown here.

<?
 $str = 'What is 5 plus three?What is 4 plus three?What is 4 plus two?';

$replacees = [
'/What is (.*?) plus three\?/',
'/What is (.*?) plus two\?/',

];
$replacers = [
 'I know $1 and 3.',
 'I know $1 and 2.',

];

print_r( preg_replace($replacees, $replacers, $str) );

I just flipped off the code and this is working now.

answered Dec 21, 2015 at 9:53

Sandeep J Patel

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1 Comment

Robbie Over a year ago

While this does work, I'd rather not have to worry about positions, since my example is really a simplified one to make understanding the issue easier.

Halayem Anis · Accepted Answer · 2015-12-21 09:48:00Z

1

You should make global searching and as i see you changed last number word, so the code is:

/(?:What is ([\d])* plus (?:[\w]+)\?)/g

Of course you can make array of one, two, etc and replace it. Example:

$arrayN = array('one'=>1, 'two'=>2, 'three'=>'3');

Then change the expression like:

/(?:What is ([\d])* plus ([\w]+)\?)/g

and add to replace string:

I know $1 and $2.

All word numbers change to numbers.

edited Dec 21, 2015 at 9:48

Halayem Anis

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answered Dec 21, 2015 at 9:37

Dmitry Shiyanov

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3 Comments

Halayem Anis Over a year ago

Welcome to SO Dmitry :) +1 for your first answer, bravo :)

Robbie Over a year ago

While that seems to be working. How would I do something similar that matches every character? For example if I had: 'What is 5five plus three?What is 4four plus three?What is 4 plus two?'

Dmitry Shiyanov Over a year ago

See thу text below: <? $str = 'What is 5 plus three?What is 4 plus three?What is 4 plus two?'; $arrayNymbers = array('one'=>1, 'two'=>2, 'three'=>3, 'four'=>4, 'five'=>5, 'six'=>6, 'seven'=>7, 'eight'=>8, 'nine'=>9, 'zero'=>0); $replacees = "/(?:What is ([\d])* plus ([\w]+)\?)/g"; $replacers = 'I know $1 and '.$arrayNumbers[$2].'.'; print_r(preg_replace($replacees, $replacers, $str) ); Try it

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