PHP Traps: string and numeric comparisons

The comparison operators in PHP are a bit weird and prone to errors, and now the comparison rules are listed:

1, when the size comparison of two characters, is compared to the ASCII size of the two characters-this article is easy to understand.

2, when the size comparison of two strings, is starting from the first character, respectively, the corresponding ASCII size, as long as from a corresponding position, where one string of the current position of the character is greater than the other string corresponding position character, that is, the direct identification of the two string size, such as ' ba ' > ' AZ '--that's what we all know.

Then ' 10 ' compared with ' a ', of course, the same, first of ' 1 ' and ' a ' ASCII code comparison, ' a ' large.

3, when a number and a string/character size comparison, the system first attempt to convert this string/character to integer/float , and then compare, such as ' 12bsd ' transformation to A,' a ' transformation to 0, It is important to note that the corresponding ASCII code value is not compared to the size of the number.

The so-called $str= "*"

$str >=0 && $str <=7 is always true .

In fact, the same reason, ' a ' +10 result is also 10.

and easy to ignore: 0 and any string comparison that is not converted to a number (operator = = =), returns TRUE.

Finally, the following results will appear:

1 var_dump (' 1000000 ' < ' a ');    Result:boolean true2 var_dump (' a ' <1);            Result:boolean true3 var_dump (1< ' 1000000 ');      Result:boolean true