This tutorial describes a small method which calculates the real width of a string and lets you create better looking preview texts!

Measuring string width

PHP offers several methods to measure a string width. You can use the built in method ImageFontWidth to measure the width of a string using the built in PHP fonts. This is quite easy and works well if you want to create a captcha or something similar, using the PHP fonts.

But there’s another method which you can easily use to get the complete bounding box of a true type font string. It’s called imagettfbbox. The return value is an array which contains several values needed for a bounding box.

The trimming method

As you’ve probably seen on the picure at the beginning of the article, I needed a method that cuts off a string after a certain width and adds a string to indicate that the text isn’t completely shown. Here’s some code:

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function trim_by_width($text,$width,$font_file,$font_size=7,$append_string = '...')
{
	$append_string_box = imagettfbbox($font_size,0,$font_file,$append_string);
	$append_string_width = $append_string_box[2];
 
	$str_len = strlen($text);
	for ($i = 0; $i<=$str_len; $i++)
	{
		$trimmed_text = substr($text,0,$i);
		$bounding_box = imagettfbbox($font_size,0,$font_file,$trimmed_text);
		$trimmed_text_width = $bounding_box[2];
		if ($trimmed_text_width + $append_string_width > $width && $i > 0)
		{
			$str_to_return = substr($trimmed_text,0,strlen($trimmed_text)-1);
			if ($trimmed_text_width != $str_len)
			{
				$str_to_return .= $append_string;
			}
			return $str_to_return;
		}
	}
	return $text;
}

$trimmed_text = trim_by_width($text, $width, $font_file, $font_size, $append_string='...');

$text:
The first parameter is the string which you want to trim

$width:
This defines the maximum width of the text in pixels! Not in characters or anything else

$font_file:
Here you have to specify the location of your true type font file.

$font_size:
The font size you want to use. Please note that unit depends on the version of the GD library you're using. GD1 uses pixels, whereas GD2 uses points

$append_string:
An optional string to define the text appended at the end of a trimmed text. By default set to "..."

An example

You can call the method like this:

echo trim_by_width('this is a long text',55,dirname(__FILE__) . '/verdana.ttf',8);

It assumes that the file verdana.ttf is in the same directory as the php script. It will cut the text “this is a long text” after 55 pixels.

That’s it!