How to convert string to boolean in PHP?

Given a string and the task is to convert given string to its boolean. Use filter_var() function to convert string to boolean value.

Examples:

Input  : $boolStrVar1 = filter_var('true', FILTER_VALIDATE_BOOLEAN); 
Output : true

Input  : $boolStrVar5 = filter_var('false', FILTER_VALIDATE_BOOLEAN);
Output : false

Approach using PHP filter_var() Function: The filter_var() function is used to filter a variable with specified filter. This function is used to both validate and sanitize the data.

Syntax:

filter_var( var, filterName, options )

Parameters: This function accepts three parameters as mentioned above and described below:

  • var: It is the required field. It denotes the variable to filter.
  • filterName: It is used to specify the ID or name of the filter to use. The default filter is FILTER_DEFAULT. It is optional field.
  • options: It is used to specify one or more flags/options to use. Check each filter for possible options and flags. It is also optional field.

Return Value: Returns the filtered data on success, or False on failure.

Program:

filter_none

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<?php
// PHP program to illustrate the conversion
// of String to Boolean value
  
// The below statement returns the boolean value true
var_dump(filter_var('true', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('1', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('on', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('yes', FILTER_VALIDATE_BOOLEAN));
  
// The below statement returns the boolean value false
var_dump(filter_var('false', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('0', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('off', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('no', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('', FILTER_VALIDATE_BOOLEAN));
  
?>

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Output:

bool(true)
bool(true)
bool(true)
bool(true)
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)


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