PHP Cookbook

1.7. Interpolating Functions and Expressions Within Strings

Problem

You want to include the results of executing a function or expression within a string.

Solution

Use the string concatenation operator (.) when the value you want to include can’t be inside the string:

print 'You have '.($_REQUEST['boys'] + $_REQUEST['girls']).' children.';
print "The word '$word' is ".strlen($word).' characters long.';
print 'You owe '.$amounts['payment'].' immediately';
print "My circle's diameter is ".$circle->getDiameter().' inches.';

Discussion

You can put variables, object properties, and array elements (if the subscript is unquoted) directly in double-quoted strings:

print "I have $children children.";
print "You owe $amounts[payment] immediately.";
print "My circle's diameter is $circle->diameter inches.";

Direct interpolation or using string concatenation also works with heredocs. Interpolating with string concatenation in heredocs can look a little strange because the heredoc delimiter and the string concatenation operator have to be on separate lines:

print <<< END
Right now, the time is 
END
. strftime('%c') . <<< END
 but tomorrow it will be 
END
. strftime('%c',time() + 86400);

Also, if you’re interpolating with heredocs, make sure to include appropriate spacing for the whole string to appear properly. In the previous example, “Right now the time” has to include a trailing space, and “but tomorrow it will be” has to include leading and trailing spaces.

See Also

For the syntax to interpolate variable variables (like ${"amount_$i"}), see Recipe 5.5; documentation on the string concatenation operator at http://www.php.net/language.operators.string.