How Does PHP Handle True/False Comparisons with Non-Boolean Operands?

Understanding True/False Comparisons in PHP

In PHP, comparing true and false values is a fundamental aspect of programming. However, the specific behavior of these comparisons can sometimes be confusing, particularly when it involves non-boolean operands.

PHP's Internal Handling of True/False Values

Unlike some other programming languages, PHP does not explicitly define true as 1 and false as 0. Internally, PHP uses the concept of "truthy" and "falsey" values to determine the boolean outcome of a comparison.

Truthiness and Falseyness in Expressions

When evaluating an expression in an if statement or any other context where a conditional check is made, PHP applies the following rules:

• All non-empty strings, non-zero numbers, non-empty arrays, and objects are considered "truthy."

• The following values are explicitly considered "falsey":

  • false
  • 0
  • 0.0
  • empty strings (including '0')
  • empty arrays
  • objects with no member variables
  • NULL
• The absence of a defined value (uninitialized variables) is also interpreted as "falsey."

How PHP Recognizes "a" as 1

In the example given:

if("a"){
   echo "true";
}

PHP interprets the string "a" as a non-empty string, which is considered truthy. Therefore, the if statement evaluates to true, and "true" is echoed.

Additional Notes

It's important to note that the comparison rules mentioned above are also applied to arithmetic and bitwise operations. For example, if "a" is treated as a truthy value, the expression "1 a" will yield 2, while "1 - a" will yield 0.

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