Comparison of numbers and strings in PHP

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Comparison operations in PHP The symbols are a bit weird and easy to make mistakes. Here are the comparison rules:

1. When two characters are compared in size, the ASCII code size of the two characters is compared - this is easy to understand.

2. When two strings are compared in size, they start from the first character and compare the corresponding ASCII sizes. As long as they start from a certain corresponding position, the current position of one of the strings is If the character is larger than the corresponding character in another string, the size of the two strings can be directly determined, such as 'ba'>'az' - everyone knows this.

Then comparing '10' and 'a', of course it is still the same. First compare '1' and 'a' ASCII code, 'a' is larger.

3. When a number is compared with a string/character, the system first tries to convert the string/character into an integer/floating point type, and then compares it. For example, '12bsd' is converted to 12. 'a' is converted to 0. It must be noted that at this time, the corresponding ASCII code value is not compared with the number.

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

And it is easy to ignore: 0 is compared with any string that cannot be converted into a number (the operator is ==), and all returns true.

The following result will appear in the end:

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

It is still a little different from the conventional thinking. .

Reprint address: http://www.cnblogs.com/lwbqqyumidi/archive/2013/01/31/2887086.html

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