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

Comparing Strings
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The length parameter can be used to specify either a number of characters to return
(if it is positive) or the end character of the return sequence (if it is negative). For
example,
substr($test, 0, 4);
returns the first four characters of the string—namely, Your.The code
echo substr($test, 5, -13);
returns the characters between the fourth character and the thirteenth-to-last
character—that is, customer service.The first character is location 0. So location 5 is
the sixth character.
Comparing Strings
So far, we’ve just shown you how to use == to compare two strings for equality.You can
do some slightly more sophisticated comparisons using PHP.We’ve divided these comparisons
into two categories for you: partial matches and others.We deal with the others
first and then get into partial matching, which we need to further develop the Smart
Form example.
Performing String Ordering: strcmp(), strcasecmp(), and
strnatcmp()
The strcmp(), strcasecmp(), and strnatcmp() functions can be used to order strings.
This capability is useful when you are sorting data.
The prototype for strcmp() is
int strcmp(string str1, string str2);
The function expects to receive two strings, which it compares. If they are equal, it will
return 0. If str1 comes after (or is greater than) str2 in lexicographic order, strcmp()
will return a number greater than zero. If str1 is less than str2, strcmp() will return a
number less than zero.This function is case sensitive.
The function strcasecmp() is identical except that it is not case sensitive.
The function strnatcmp() and its non–case sensitive twin, strnatcasecmp() compare
strings according to a “natural ordering,” which is more the way a human would do
it. For example, strcmp() would order the string 2 as greater than the string 12 because
it is lexicographically greater. strnatcmp() would order them the other way around.You
can read more about natural ordering at http://www.naturalordersort.org/