12

How can I convert 

ereg_replace(".*\.(.*)$","\\1",$imgfile);

to

preg_replace... ?

?

I'm having trouble with it?

Daniel Vandersluis
  • 91,582
  • 23
  • 169
  • 153
sml
  • 133
  • 1
  • 1
  • 6

3 Answers3

23

You should know 4 main things to port ereg patterns to preg:

  1. Add delimiters(/): 'pattern' => '/pattern/'

  2. Escape delimiter if it is a part of the pattern: 'patt/ern' => '/patt\/ern/'
    Achieve it programmatically in following way:
    $ereg_pattern = '<div>.+</div>';
    $preg_pattern = '/' .addcslashes($ereg_pattern, '/') . '/';

  3. eregi(case-insensitive matching): 'pattern' => '/pattern/i' So, if you are using eregi function for case insenstive matching, just add 'i' in the end of new pattern('/pattern/').

  4. ASCII values: In ereg, if you use number in the pattern, it is assumed that you are referring to the ASCII of a character. But in preg, number is not treated as ASCII value. So, if your pattern contain ASCII value in the ereg expression(for example: new line, tabs etc) then convert it to hexadecimal and prefix it with \x.
    Example: 9(tab) becomes \x9 or alternatively use \t.

Hope this will help.

Ben Miller - Remember Monica
  • 510
  • 3
  • 22
Sumoanand
  • 8,835
  • 2
  • 47
  • 46
11
preg_replace("/.*\.(.*)$/", "\\1", "foo.jpg")

I don't know why PHP requires the / delimiters. The only reason Perl, JS, etc. have them is that they allow regex literals, which PHP doesn't.

Matthew Flaschen
  • 278,309
  • 50
  • 514
  • 539
  • 8
    It is because they opt to use the single string to provide both the modifier and the regex pattern. `"/[a-z]/i"`. – kennytm Apr 08 '11 at 16:09
  • See https://www.php.net/manual/en/regexp.reference.delimiters.php .. for example, `$a = 'string/with/slashes'; $b = preg_replace('#/with/#', '-without-', $a);` is valid, sets `$b` to `string-without-slashes` and you do not have to escape the `/` in the regex given to `preg_replace`. – Neek Jul 09 '19 at 07:05
1

delimiters, add any char to beginning and end of expression, in this case, and by tradition, the '/' character preg_replace('/.*\.(.*)$/',"\\1",$imgfile); The regex isn't very good, better to use strrpos and take substr().

Regex is slow, use this. $extension=substr($imgName,strrpos($imgName,'.'));

Jimmy Ruska
  • 468
  • 2
  • 9
  • I know but having this problem; preg_replace() [function.preg-replace]: Unknown modifier '$' in C:\wamp\www.. – sml Mar 14 '10 at 21:48
  • Yes, my bad, also the editing seems to destroy the expression. In the end better to use a substr() in this case. You could also use preg_match. – Jimmy Ruska Mar 14 '10 at 21:52
  • You can escape your code with backticks (see http://stackoverflow.com/editing-help). The $ fix looks good. – Matthew Flaschen Mar 14 '10 at 21:57