Hello people

I would like to use regular expression to check if a string contains the definition of background-image:url(<file>.png) attribute

that is in the following strings the attribute will be found:
style="background-image: url('test.png')"
style="background-image: url('/Folder/test.png')"
style="background-image: url('./folder/Test.png')"

I tried the following but it doesn't work:
PHP Code:
However count($matches[0]) is always zero

can anyone see what is wrong with the regular expression, or maybe something is wrong in my examples