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Top Forums UNIX for Dummies Questions & Answers If statement with two boolean conditions Post 302838469 by Don Cragun on Monday 29th of July 2013 08:48:21 PM
Old 07-29-2013
There are utilities named true and false on UNIX and Linux systems, but you aren't using them in your if statement. If you wanted to use them, the if statement would be:
Code:
if true && ! false
then    echo true
else    echo false
fi

The if statement you had was using the test utility to evaluate whether or not "true" was <not an empty string> which evaluates to true and the second test utility invocation to evaluate whether or not NOT ("false" was <not an empty string>) which evaluates to false. Since both did not evaluate to true, the AND of the two tests evaluates to false and you executed the "else" branch of your if statement.
 

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IS_STRING(3)								 1							      IS_STRING(3)

is_string - Find whether the type of a variable is string

SYNOPSIS
bool is_string (mixed $var) DESCRIPTION
Finds whether the type given variable is string. PARAMETERS
o $var - The variable being evaluated. RETURN VALUES
Returns TRUE if $var is of type string, FALSE otherwise. EXAMPLES
Example #1 is_string(3) example <?php $values = array(false, true, null, 'abc', '23', 23, '23.5', 23.5, '', ' ', '0', 0); foreach ($values as $value) { echo "is_string("; var_export($value); echo ") = "; echo var_dump(is_string($value)); } ?> The above example will output: is_string(false) = bool(false) is_string(true) = bool(false) is_string(NULL) = bool(false) is_string('abc') = bool(true) is_string('23') = bool(true) is_string(23) = bool(false) is_string('23.5') = bool(true) is_string(23.5) = bool(false) is_string('') = bool(true) is_string(' ') = bool(true) is_string('0') = bool(true) is_string(0) = bool(false) SEE ALSO
is_float(3), is_int(3), is_bool(3), is_object(3), is_array(3). PHP Documentation Group IS_STRING(3)
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