Error condition when using preg_match in php?

Question

I have a sample string:

revision
revision-2
revision-3
revision-n...
autosave

and php code

if(preg_match('/revision/', $str)) {
   echo "Edit 1";
}elseif(preg_match('/revision-(.+?)/', $str)) {
   echo "Edit $1";
}else {
   echo "Auto save";
}

But result null, how to fix it?

http://www.9lessons.info/2013/10/understanding-regular-expression.html#more This is the best and easiest regular expression tutorial can help you in debugging — Veerendra, Nov 13 '13 at 09:36
What do you mean by "result null"? This code echoes "Edit 1" when I execute it. What is is you are trying to achieve here? — ZeWaren, Nov 13 '13 at 09:36
maybe You have this problem: http://stackoverflow.com/questions/8859363/warning-preg-match-internal-pcre-fullinfo ??? — Adam, Nov 13 '13 at 09:40

score 1 · Answer 1 · answered Nov 13 '13 at 09:38

You're not capturing your pattern anywhere. You need to do that:

$str = 'revision-14';
if(preg_match('/revision-(.*)/', $str, $matches)) 
{
   echo "Edit ".$matches[1];
}
elseif(preg_match('/revision/', $str)) 
{
   echo "Edit 1";
}
else 
{
   echo "Auto save";
}

also note, that /revision/ is less restrictive, so you need to place more-restrictive condition first

score 1 · Accepted Answer · answered Nov 13 '13 at 09:41

I think that what you are trying to do is this:

if(preg_match('/^revision-(?[0-9]+)$/', $str, $matches)) {
   echo "Edit ". $matches[0];
} elseif(preg_match('/revision/', $str)) {
   echo "Edit 1";
} else {
   echo "Auto save";
}

Explanation:

̛'^' means 'starts with'
(? ) tells the regular expression to save the match it encloses
[0-9] means all characters from 0 to 9
'+' means one or more times
'$' means 'ends with'

Put that all together, and you have a regular expression meaning If the string contains only 'revision', a dash, and a number, save the number and output it as the Edit number. Otherwise output 'Auto Save'.

score 0 · Answer 3 · answered Nov 13 '13 at 09:39

The first if(preg_match('/revision/', $str)) will match all the cases except "autosave". You may want /^revision$/ to match "revision" exclusively.
I guess you expect echo "Edit $1" to output the (.+?) match. That's not how it works. You have to capture the match using the third argument to preg_match:
```
if (preg_match('/revision-(.+?)/', $str, $match)) {
    echo "Edit $match[1]";
}
```

score 0 · Answer 4 · answered Nov 13 '13 at 09:46

0

Alternative:

You could use explode to find the value. If your output remains the same that is.

$match = end(explode('-', $str));

This will assign the value after '-' to $match.

answered Nov 13 '13 at 09:46

Fyntasia

1,133
6
19

score 0 · Answer 5 · answered Nov 13 '13 at 10:02

There might be some problem in pattern string

hope below pattern will resolve ur problem.

preg_match('\'revision-2\'', 'revision revision-2 revision-3 revision-n... autosave', $matches);

There is one useful online link is also available to Perform a regular expression match. This can also be helpful for you :

http://www.functions-online.com/preg_match.html

Happy Coding :)

Error condition when using preg_match in php?

5 Answers5