问题
var_dump(md5('240610708') == md5('QNKCDZO'));
Output:
bool(true)
Example: http://3v4l.org/2vrMi
回答1:
md5('240610708') 's result is 0e462097431906509019562988736854.
md5('QNKCDZO') 's result is 0e830400451993494058024219903391.
They are both float number format strings (numerical strings), and if you use == in php, when compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically.
Both of the strings are converted to 0 when compared with ==, if you want to compare them as string, remember to use ===(strict comparison) instead.
See: PHP expresses two different strings to be the same
回答2:
You need to use the type-sensitive comparison operator ===.
The hashes evaluate to 0e462097431906509019562988736854 and 0e830400451993494058024219903391, respectively. When you use ==, each is converted to a numeric representation because of the e (scientific notation), so they each become 0. 0 == 0 is true.
On the other hand, this:
md5('240610708') === md5('QNKCDZO')
returns false because the string values are different. === forces type-sensitive comparison.
来源：https://stackoverflow.com/questions/22140204/why-md5240610708-is-equal-to-md5qnkcdzo