PHP determines whether the date format is valid

Implementation method

functionIsDate ($dateString ) {    return Strtotime(Date(' y-m-d ',Strtotime($dateString)) ) ===Strtotime($dateString );} Echo $this->isdate (' 2014-11-19 ')? ' True ': ' false ';Echo' </br> ';Echo $this->isdate (' 2014-11-32 ')? ' True ': ' false ';Echo' </br> ';Echo $this->isdate (' 2014-a-b ')? ' True ': ' false ';Echo' </br> ';Echo $this->isdate (' 2014-1-1 ')? ' True ': ' false ';Echo' </br> ';Echo $this->isdate (' 2014-01-01 ')? ' True ': ' false ';/*result Truefalsefalsetruetrue*/    

Date (' y-m-d ', Strtotime ($dateString)) This code converts the input time string to a Unix timestamp (since 1970-1-1 0:0:0) and then back to the date string. If the date string entered is not properly formatted, the value before the conversion is inconsistent with the converted value, that is, the date (' y-m-d ', Strtotime ($dateString)) = = = $dateString The result of this code will be false. Then why write the above code strtotime (date (' y-m-d ', Strtotime ($dateString))) = = = Strtotime ($dateString)? Because the code is written as date (' y-m-d ', Strtotime ($dateString)) = = $dateString So, if the value of $datestring is 2014-1-1 this format (a valid time string), The returned result will also be false, because date (' y-m-d ', strtotime (' 2014-1-1 ') returns the result as 2014-01-01, and if the month and date are single digit, it will be automatically 0 in the front, From the aspect of string comparison, 2014-1-1 is obviously not equal to 2014-01-01, so we need to add strtotime to the outer layer, convert the date on both sides to the Unix timestamp, and then compare.

Original address: http://chhblog.com/article/294.html

PHP determines whether the date format is valid