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Web Technologies-I

Notes The Soundex and Metaphone algorithms each yield a string that represents roughly how a
word is pronounced in English. To see whether two strings are approximately equal with these
algorithms, compare their pronunciations. You can compare Soundex values only to Soundex
values and Metaphone values only to Metaphone values. The Metaphone algorithm is generally
more accurate, as the following example demonstrates:
$known = “Pradip”; $query = “Phred”; if (soundex($known) == soundex($query)) { print “soundex:
$known sounds $query<br>”; } else { print “soundex: $known does not sound like $query<br>”; }
if (metaphone($known) == metaphone($query)) { print “metaphone: $known sounds $query<br>”;
} else { print “metaphone: $known does not sound like $query<br>”; } soundex: Pradip does not
sound like Phred metaphone: Pradip sounds like Phred

The similar_text( ) function returns the number of characters that its two string arguments have
in common. The third argument, if present, is a variable in which to store the commonality as a
percentage:
$string_1 = “XYZ”; $string_2 = “AXBYZ”; $common = similar_text($string_1, $string_2, $percent);
printf(“They have %d chars in common (%.2f%%).”, $common, $percent); They have 13 chars in
common (89.66%).
The Levenshtein algorithm calculates the similarity of two strings based on how many characters
you must add, substitute, or remove to make them the same. For instance, “cat” and “cot” have
a Levenshtein distance of 1, because you need to change only one character (the “a” to an “o”)
to make them the same:
$similarity = levenshtein(“cat”, “cot”); // $similarity is 1
This measure of similarity is generally quicker to calculate than that used by the similar_text( )
function. Optionally, you can pass three values to thelevenshtein( ) function to individually weight
insertions, deletions, and replacements for instance, to compare a word against a contraction.

This example excessively weights insertions when comparing a string against its possible
contraction, because contractions should never insert characters:
echo levenshtein(‘would not’, ‘wouldn\’t’, 500, 1, 1);

5.7 Manipulating and Searching Strings

PHP has many functions to work with strings. The most commonly used functions for searching
and modifying strings are those that use regular expressions to describe the string in question.
The functions described in this do not use regular expressions. They are faster than regular
expressions, but they work only when you are looking for a fixed string.

5.7.1 Substrings
If you know where in a larger string the interesting data lies, you can copy it out with the substr( )
function:
$piece = substr(string, start [, length ]);
The start argument is the position in string at which to begin copying, with 0 meaning the start of
the string. The length argument is the number of characters to copy (the default is to copy until
the end of the string).

Example:

$name = “Pradip Kumar”; $fluff = substr($name, 6, 4); // $fluff is “lint” $sound = substr($name,
11); // $sound is “tone”

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