PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Matching and Replacing Substrings with String Functions
121
The function strstr(), which is the most generic, can be used to find a string or
character match within a longer string. In PHP, the strchr() function is exactly the
same as strstr(), although its name implies that it is used to find a character in a string,
similar to the C version of this function. In PHP, either of these functions can be used to
find a string inside a string, including finding a string containing only a single character.
The prototype for strstr() is as follows:
string strstr(string haystack, string needle);
You pass the function a haystack to be searched and a needle to be found. If an exact
match of the needle is found, the function returns the haystack from the needle
onward; otherwise, it returns false. If the needle occurs more than once, the returned
string will start from the first occurrence of needle.
For example, in the Smart Form application, you can decide where to send the email
as follows:
$toaddress = ‘feedback@example.com’; // the default value
// Change the $toaddress if the criteria are met
if (strstr($feedback, ‘shop’))
$toaddress = ‘retail@example.com’;
else if (strstr($feedback, ‘delivery’))
$toaddress = ‘fulfillment@example.com’;
else if (strstr($feedback, ‘bill’))
$toaddress = ‘accounts@example.com’;
This code checks for certain keywords in the feedback and sends the mail to the appropriate
person. If, for example, the customer feedback reads “I still haven’t received delivery
of my last order,” the string “delivery” will be detected and the feedback will be sent
to fulfillment@example.com.
There are two variants on strstr().The first variant is stristr(), which is nearly
identical but is not case sensitive.This variation is useful for this application because the
customer might type "delivery", "Delivery", "DELIVERY", or some other mixed-case
variation.
The second variant is strrchr(), which is again nearly identical, but returns the
haystack from the last occurrence of the needle onward.
Finding the Position of a Substring: strpos() and strrpos()
The functions strpos() and strrpos() operate in a similar fashion to strstr(),
except, instead of returning a substring, they return the numerical position of a needle
within a haystack. Interestingly enough, the PHP manual recommends using
strpos() instead of strstr() to check for the presence of a string within a string
because it runs faster.