php - Regex Lookarounds, prevent ahead and behind -


i have regex cannot working right. using pcre(php) run it.

the regex looks inch measurements written fractions using forward slash separate numerator , denominator. ex 1 3/8in or 19 15/16"

it match 12 1/2" here:

a product description 12 1/2" in it. 

but want not match if measurement part of dimension, ie has x before or after , matches format: 19 3/4" x 19 5/8"

example text matching incorrectly:

product description 19 3/4" x 19 5/8" in it. 

this matches 5/8" when supposed ignore of because of x in there.

my regex knocks off measure left of x, ignores whole number on right side. lookbehind capture 5/8" example above. need ignore both sides of dimension , match measurements themselves. using negative ahead , behind match x.

regex:

/\s+(?<!x\s)\d*\s?\d+\/\d+"*\s*(in|")(?!\d*\s?x)\s*/i 

i ran through regex101.com's debugger , still can't figure out. reading.

with pcre/php use (*skip)(*fail)

\d*\s?\d+\/\d+"*\s*(in|")\sx\s\d*\s?\d+\/\d+"*\s*(in|")(*skip)(*fail)|\d*\s?\d+\/\d+"*\s*(in|") 

demo


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