String refers to a set of zero or more characters. Because PHP has been developed for web since its inception.
Because in website development, string processing is a highlight of PHP. In php, 1 is a string, 2 is an arrayfunction, there are many of them and they are very easy to use.
Simply put, strings are what we say every day. For example, I want to say "I want to learn PHP language development" or "I want to create a good website" and so on. It's all the characters I want to express that people can see. Generally visible text, HTML tags, special characters, English, etc., can all be considered strings.
The characters mentioned here mainly include the following types:
1. Number type , such as 1, 11, 111, etc.
2. Letter type, such as a, df, msn, etc.
3. Special types, such as #, $, ^, &, etc.
4. Invisible characters, such as \n (line feed character), \r (carriage return character), \t (Tab character), etc.
Invisible characters are a special group of characters used to control string formatted output. They are invisible in the browser. Generally, only string output can be seen. result.
The following is a simple example of a string:
<?php echo "goods \r apple \n sony"; //输出字符串 ?>
The output result is:
goods apple sony
Tips: The result of running the example in the browser is, "goods apple sony" , you need to click the "right mouse button" in the browser / select "View web page source code" to view the output of the string.
Picture similar to the following:
How to convert a value into a string?
#A value can be converted to a string by preceding it with (string) or using the strval() function. In an expression that expects a string, it is automatically converted to string. This conversion occurs, for example, when using the functions echo or print, or when comparing a variable to a string. Types and type conversions can be better explained below. You can also refer to the function settype().
A boolean value of TRUE is converted into a string of "1". Boolean FALSE is converted to "" (empty string). This conversion can be done between boolean and string.
An integer or float is converted to a numeric literal-style string (including the exponent part of the float). Floating point numbers using exponential notation (4.1E+6) can also be converted.
What needs to be noted here is: NULL is always converted into an empty string.
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