Which PHP functions can return boolean values?

PHP provides a variety of functions that return Boolean values, including: boolval(): Convert values ​​to Boolean values. is_bool(): Checks whether the value is a Boolean value. empty(): Check whether the value is empty. isset(): Checks whether the variable is defined and assigned a value. strcmp(): Compares two strings for equality. strncmp(): Compares two strings for equality within a specified length. strlen(): Returns the length of the string.

PHP functions that return Boolean values

The PHP language provides many functions that can return Boolean values ​​(true or false). These functions are useful for determining conditions, controlling flow, and performing binary operations.

Common PHP Boolean functions

• boolval(): Convert any value to a Boolean value.
• is_bool(): Checks whether the value is a Boolean value.
• empty(): Check whether the value is empty (value is false, 0, empty string or empty array).
• isset(): Checks whether the variable is defined and has a value assigned.
• strcmp(): Compares two strings for equality (returns 0 for equality).
• strncmp(): Compares two strings for equality (within the specified length).
• strlen(): Returns the length of the string (the result is 0 indicating an empty string).

Practical cases

The following are some practical cases using PHP Boolean functions:

Check whether the value is a Boolean value:

$value = true;

if (is_bool($value)) {
  echo "变量 $value 是布尔值";
} else {
  echo "变量 $value 不是布尔值";
}

Convert the value to Boolean:

$value = "hello";

$boolValue = boolval($value); // 将 "hello" 转换为 true

if ($boolValue) {
  echo "字符串 \"hello\" 求值后为 true";
}

Check if the variable exists and has been assigned a value:

if (isset($variable)) {
  echo "变量 $variable 已定义并已赋值";
} else {
  echo "变量 $variable 未定义或未赋值";
}

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