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Editorial Team
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Asked: 2026-05-14T21:43:05+00:00

I am have completed javascript validation of a form using Regular Expressions and am

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I am have completed javascript validation of a form using Regular Expressions and am now working on redundant verification server-side using PHP.

I have copied this regular expression from my jscript code that finds dollar values, and reformed it to a PHP friendly format:

/\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/

Specifically:

if (preg_match("/\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/", $_POST["cost"])){}

While the expression works great in javascript I get :

Warning: preg_match() [function.preg-match]: Compilation failed: nothing to repeat at offset 1

when I run it in PHP. Anyone have a clue why this error is coming up?

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1 Answer

  1. Editorial Team

    you have to double escape the $.

    if (preg_match("/\\\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/", $_POST["cost"])){}

    just putting \$ will have php escape the $ from starting a variable. You also have to add another escaped \ (\\) in front. Or you could just use single quotes so php doesn’t interpret the $ as the start of a variable.

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