Finding the Last Occurrence of a String - PHP

Thestrrpos()function finds the last occurrence of a string, returning its numerical position. Its prototype follows:

int strrpos(string str, char substr [, offset])

The optional parameteroffsetdetermines the position from whichstrrpos()will begin searching. Suppose you wanted to pare down lengthy news summaries, truncating the summary and replacing the truncated component with an ellipsis. However, rather than simply cut off the summary explicitly at the desired length, you want it to operate in a user-friendly fashion, truncating at the end of the word closest to the truncation length. This function is ideal for such a task. Consider this example:

<?php
    // Limit $summary to how many characters?
    $limit = 100;

    $summary = <<< summary
    In the latest installment of the ongoing Developer.com PHP series,
    I discuss the many improvements and additions to
    <a href="http://www.php.net">PHP 5's</a> object-oriented
    architecture.
summary;

    if (strlen($summary) > $limit)
        $summary = substr($summary, 0, strrpos(substr($summary, 0, $limit),
               ' ')) . '...';
    echo $summary;
?>

This returns the following:

--------------------------------------------
In the latest installment of the ongoing Developer.com PHP series,
I discuss the many...
--------------------------------------------

Replacing All Instances of a String with Another String

Thestr_replace()function case sensitively replaces all instances of a string with another. Its prototype follows:

mixed str_replace(string occurrence, mixed replacement, mixed str [, int count])

Ifoccurrenceis not found instr, the original string is returned unmodified. If the optional parametercount is defined, onlycount occurrences found instrwill be replaced.

This function is ideal for hiding e-mail addresses from automated e-mail address retrieval programs:

<?php
    $author = jason@example.com;
    $author = str_replace("@","(at)",$author);
    echo "Contact the author of this article at $author.";
?>

This returns the following:

--------------------------------------------
Contact the author of this article at jason(at)example.com.
--------------------------------------------

The functionstr_ireplace()operates identically tostr_replace(), except that it is capable of executing a case-insensitive search.