Searching for words inside a string by using stristr & strstr function

$haystack="myuserid@example.com";
$needle="@";
echo strstr($haystack,$needle,false);// @example.com

Output is

@example.com

Syntax

echo strstr($haystack,$needle,$before);

$haystack

Required: Input string ( main string for searching )

$needle

Required: used to search the first occurrence inside Input string

$before

Optional: default FALSE, if set to TRUE then output returns the string before the first occurrence of $needle ( excluding the $needle )

Output is the part of string after the needle ( if $before is FALSE ) or before the needle. FALSE is returned if matching is not found.

This is case sensitive search. Use stristr() for case in-sensitive search

$haystack="myuserid@example.com";
$needle="@";
echo strstr($haystack,$needle,true);// myuserid

Output is

myuserid

Example of strstr()

$haystack="Welcome to plus2net.com to learn PHP";
$needle="to";
echo strstr($haystack,$needle);// to plus2net.com to learn PHP

Output is

to plus2net.com to learn PHP

Uses of strstr

We can find out existence of a word or combination of words in a string. For example we don't want some words to be posted by the user while submitting any message or text to the system. We can check the existence of the word (case insensitive checking) by using stristr() function and know the presence of the string.

For a case sensitive checking we can use strstr function.

Another example is checking of links posted by users in a site where any one can post jokes. Some people were posting links in the text area to their sites. To prevent that , stristr function is used to check the presence of https:// in the posted message. Or it can be checked the presence of <a in the posted string to identify a link. Here is the syntax of this function.

string stristr (main string , checking string)

This function returns true if the checked string is found within the main string. Now here is a code which uses stristr function and returns true after checking the word.

$main_string="This is a test string <a href=https://www.plus2net.com>with a link</a> to plus2net";

if(stristr($main_string,"https://")){

echo "String contains a link or the text https:// inside it ";}					

else {

echo "String does not contains a link or the text https:// inside it ";}

Let us try to collect domain part from the email address by using strstr function.

$email = "myname@mysitenamehere.com";
$domain = strstr ($email, "@");
echo  $domain; // prints @mysitenamehere.com

We can also use split command to get the domain part from email address.

Searching Blank space inside a string

$string='first second';
if (strstr($string,' ')) {
echo " There is blank space present inside the string ";
}else{
echo " There is NO blank space present inside the string ";
}

The output is

 There is blank space present inside the string

String Functions Searching and replacing a set of strings strlen(): Length of the string nl2br() To add Line break

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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strstr():Searching for a match inside a string

Example of strstr()

Uses of strstr

Searching Blank space inside a string

Subhendu Mohapatra