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Handling Strings and Arrays in PHP

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In PHP, two types of data (strings and arrays) warrant special attention and a more complete explanation. This chapter details how and why these special data types are employed in PHP 5 with copious examples to get you started using these in your code.
This chapter is from the book

This chapter is from the book

Two data types merit some special attention—strings and arrays. We've already seen strings at work, including single- and double-quoted strings (recall also that double-quoted strings allow variable interpolation). PHP also comes packed with more string power, and we're going to dig into that in this chapter—tons of functions are built into PHP that work with strings, from sorting strings to searching them, trimming extra spaces off of them, and getting their lengths. We'll get a handle on those functions in this chapter.

Besides strings, we're also going to get a handle on arrays in this chapter. We've seen how to store data in simple variables, but there's more to the story here. Arrays can hold multiple data items, assigning each one a numeric or text index (also called a key). For example, if you want to store some student test scores, you can store them in an array, and then you can access each score in the array via a numeric index. That's great as far as computers are concerned because you can work through all the elements in an array simply by steadily incrementing that index, as you might do with a loop. In that way, you can use your computer to iterate over all the elements in an array in order to print them out or find their average value, for example.

Arrays represent the first time we're associating data items together. Up to this point, we've only worked with simple variables, but working with arrays is fundamental to PHP for such tasks as reading the data that users enter in web pages. We'll get the details on strings and arrays in this chapter, and I'll start with the string functions.

Listing of String Functions

PHP has plenty of built-in string functions. Table 3-1 lists a selection of them.

Table 3-1. The String Functions

Function

Purpose

chr

Returns a specific character, given its ASCII code

chunk_split

Splits a string into smaller chunks

crypt

Supports one-way string encryption (hashing)

echo

Displays one or more strings

explode

Splits a string on a substring

html_entity_decode

Converts all HTML entities to their applicable characters

htmlentities

Converts all applicable characters to HTML entities

htmlspecialchars

Converts special characters to HTML entities

implode

Joins array elements with a string

ltrim

Strips whitespace from the beginning of a string

number_format

Formats a number with grouped thousand separators

ord

Returns the ASCII value of character

parse_str

Parses the string into variables

print

Displays a string

printf

Displays a formatted string

rtrim

Strips whitespace from the end of a string

setlocale

Sets locale information

similar_text

Calculates the similarity between two strings

sprintf

Returns a formatted string

sscanf

Parses input from a string according to a format

str_ireplace

Case-insensitive version of the str_replace function.

str_pad

Pads a string with another string

str_repeat

Repeats a string

str_replace

Replaces all occurrences of the search string with the replacement string

str_shuffle

Shuffles a string randomly

str_split

Converts a string to an array

str_word_count

Returns information about words used in a string

strcasecmp

Binary case-insensitive string comparison

strchr

Alias of the strstr function

strcmp

Binary-safe string comparison

strip_tags

Strips HTML and PHP tags from a string

stripos

Finds position of first occurrence of a case-insensitive string

stristr

Case-insensitive version of the strstr function

strlen

Gets a string's length

strnatcasecmp

Case-insensitive string comparisons

strnatcmp

String comparisons using a "natural order" algorithm

strncasecmp

Binary case-insensitive string comparison of the first n characters

strncmp

Binary-safe string comparison of the first n characters

strpos

Finds position of first occurrence of a string

strrchr

Finds the last occurrence of a character in a string

strrev

Reverses a string

strripos

Finds the position of last occurrence of a case-insensitive string

strrpos

Finds the position of last occurrence of a char in a string

strspn

Finds the length of initial segment matching mask

strstr

Finds the first occurrence of a string

strtolower

Converts a string to lowercase

strtoupper

Converts a string to uppercase

strtr

Translates certain characters

substr_compare

Binary-safe (optionally case-insensitive) comparison of two strings from an offset

substr_count

Counts the number of substring occurrences

substr_replace

Replaces text within part of a string

substr

Returns part of a string

trim

Strips whitespace from the beginning and end of a string

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