PHP Basics Review the use and difference of echo print printf sprintf print_r var_dump
First, Echo
Echo () is not actually a function, it is a PHP statement, so you do not need to use parentheses on it. However, if you want to pass more than one argument to Echo (), a parse error occurs when you use parentheses. and echo returns void and does not return a value, so it cannot be used to assign a value.
Example:
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Php$a=Echo("55nav");//Error! Cannot be used to assign a valueEcho"55nav";//55navEcho("55nav");//55navEcho("55nav", "com");//An error occurred with parentheses that cannot pass multiple argumentsEcho"55nav", "com", "is", "web";//you can separate multiple values with commas without parentheses, and output a 55nav com is webEcho"55nav is 8 good 9 web.";//The final display is for a row of 55nav is good web, regardless of whether the line is wrapped. $fistname= "55nav"; Echo"$fistnameCOM ";//If $firstname = "55nav", 55nav com is output. Echo' $firstname com ';//because the single quotation marks are used, the $firstname value is not output, but the output $firstname com?>
Second, print
Print () is the same as Echo (), but the echo speed is a little bit faster than print. It is not actually a function, so you do not need to use parentheses on it. However, if you want to pass more than one parameter to print (), a parse error occurs when you use parentheses. Note that print always returns 1, which is different from Echo, which means you can use print to assign a value, but it doesn't make sense.
Example:
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$a Print // this is permissible. Echo $a // ?>
Three, Print_r function
The Print_r function prints easy-to-understand information about variables.
Syntax: Mixed print_r (mixed $expression [, BOOL return])
If the variable is a string, the integer or float will output its value directly, and if the variable is an array, it will output a formatted array for readability, which is the format of the key and value. Similar for object objects. Print_r has two parameters, the first is a variable, the second can be set to true, and if set to True, returns a string, otherwise returns a Boolean value of true.
Example:
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PHP $a= "55nav"; $c Print_r ($a); Echo $c; // the value of $c is true $c Print_r ($a,true); Echo $c // the value of $c is the string 55nav
Four, printf function
The printf function returns a formatted string.
Syntax: printf (format,arg1,arg2,arg++)
The parameters format is the converted format, starting with the percent sign ("%") to the end of the converted character. The following is the possible format value:
*%%– return percent symbol
*%b– binary number
*%c– characters in accordance with ASCII values
*%d– Signed decimal number
*%e– counting method (e.g. 1.5e+3)
*%u– unsigned decimal number
*%f– floating point (Local settings Aware)
*%f– floating point number (not local settings aware)
*%o– octal number
*%s– String
*%x– hexadecimal number (lowercase letter)
*%x– hexadecimal number (capital letter)
Arg1, arg2, arg++, etc. parameters will be inserted into the main string percent percent (%) Symbol. The function is executed incrementally, in the first% symbol, insert arg1, insert arg2 at the second% symbol, and so on. If the% symbol is more than the arg parameter, you must use a placeholder. After the placeholder is inserted in the% symbol, it consists of a number and a "\$". You can use numbers to specify the parameters that are displayed, see examples for details.
Example:
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printf // printf//printf// My name is com 55nav
Five, sprintf function
This function uses the same method as printf, except that the function writes the formatted string to a variable instead of the output.
Example:
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sprintf ("My name is%1\ $s%1\ $s", "55nav", "com"); // you will find nothing to output. $out sprintf ("My name is%1\ $s%2\ $s", "55nav", "com"); Echo $out; // output My name is 55nav com
vi.. Var_dump function
Function: The content, type, and length of the output variable's contents, type, or string. Commonly used to debug.
Copy the Code code as follows:
$a=100var_dump($a//$a=100.356 Var_dump($a//
