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Fundamental php type comparison philosophy

So, here is this page on the php site, which shows the result of comparing different values:

http://php.net/manual/en/types.comparisons.php

This is a useful link, but I would prefer not to visit this page every time I want to make sure that I am doing type comparisons correctly. So my question is:

Is there any basic philosophy / logic of type comparison logic in PHP?

For example, I see that for free comparison:

  • 1, -1, "1" and "-1" can be interpreted as TRUE, and 0 and "0" can be considered as FALSE;
  • Comparison of the string value of a number with the number itself with the TRUE output;

but since then he gets a little hairy trying to set a pattern.

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For casting directly to a logical, this works.

  • The entire string with a length> 0 is correct.
  • All values ​​other than 0 are true.
  • All non-empty arrays are true.
  • All objects are correct.

Then these rules for comparing variables of the same type:

  • Objects are equivalent if their properties are equal.
  • Arrays are equivalent if their keys and elements are equal.
  • Strings are equivalent if they produce the same output
  • Numbers are equivalent if they are mathematically equivalent
  • Booleans are equivalent if they have the same value.

For a variable of different types, the type that is higher in the above list is converted to one that is lower than the comparison.

Operators

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$a = array("a"=>1, "b"=>2);
$b = array("b"=>2, "a"=>1);

$a == $b; // true
$a === $b; // false

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  • __toString .
  • , , , (UPDATE), , ArrayAccess)
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:

  • PHP is designed as a web programming language, and all page input is line-based [humanoid perception] [This, by the way, is also true for JavaScript]
  • Therefore, all strings that look like numbers (is_numeric () function) pre-behave like numbers [comparison, casting].
  • This explains why extreme cases, such as "0", are first implicitly considered cast from (int) 0, but only to false.
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