I\'m trying to validate a date input by the use of regex.
if(!preg_match(\"/^[0-9]{4}\\/[0-9]{2}\\/[0-9]{2}$/\", $_POST[\'variant\'][\'sales_start\'])) {
Building from Justin's answer I wanted to add filtering for text formatted dates as well.
Allows:
etc.
"#^(((?:0?[1-9]|1[012])|(?:0?[1-9]|[12][0-9]|3[01])|([a-zA-Z]+))([.,]?[-.\\\/\s]))?(((?:0?[1-9]|1[012])|(?:0?[1-9]|[12][0-9]|3[01])|([a-zA-Z]+))([.,]?[-.\\\/\s]))?((?:20|19)[0-9]{2})$#"
I have limited the years to 19XX and 20XX in this solution, but you can modify that if needed. I'm also not allowing the year in the first position because it's not a typical user format.
Also, if you plan to use this with JS be sure to remove the extra '\' escape in the two separated segments. (I found that PHP required '/' to be escaped where JS did not)