PHP is the abbreviation of the English hypertext preprocessing language Hypertext Preprocessor. PHP is an HTML embedded language. It is a scripting language that is embedded in HTML documents and is executed on the server side. The language style is similar to C language and is widely used.
php is a scripting language that can only be run on the browser, unlike java and C# which can be run on the console
This is the php standard format
Let’s start learning Hello world is often used in programming languages
echo "hello,world";
?>
echo is the print in php and will be displayed in the browser
php can be embedded into html code
From a syntactic point of view, PHP language is similar to C language. It can be said that PHP draws on the grammatical features of C language and is improved from C language. We can mix PHP code and HTML code. Not only can we embed PHP scripts into HTML files, we can even embed HTML tags in PHP scripts.
Separate from HTML The following methods can be used:
. . . ?> Not rigorous
Just use this
. . . This is too long. .
This is like asp
About comments
PHP supports C, C++ and Unix style comments:
/* C,C++ Style multi-line comments*/
// C++ style single-line comments
# Unix-style single-line comments
The first two are still used more
echo and print PHP and The simplest interaction of HTML is achieved through print and echo statements. In actual use, the functions of print and echo are almost exactly the same. It can be said that wherever one can be used, the other can also be used. However, there is still a very important difference between the two: in the echo function, multiple strings can be output at the same time, while in the print function, only one string can be output at the same time. At the same time, the echo function does not require parentheses, so the echo function is more like a statement than a function. Let's take a look at the following example:
$a="hello";
$b="world";
echo "a","b";
print "a","b";
?>
will report an error directly
Parse error: syntax error, unexpected ','
So this is the only way
$a="hello";
$b="world";
echo "a","b";
print "a";
?>
The above will print aba
$a="hello";
$b="world";
echo $a.$b;
print $a ;
?>
will print helloworldhello
$a="hello"; is to define a string and add $ before the letter to indicate that it is a variable
And the variable type is determined by php , the key is to see what value you assign to the variable
This is similar to JavaScript's var definition of variables
$Although this form looks a bit awkward, it will be fine once you get used to it. At least you don't need to consider it when defining variables using this Type, there is no need to consider any type conversion, this is much simpler than C language
How to check what type a variable is?
Use var_dump function
$a="hello";
$b=1;
$c=1.1;
$d='h';
$e=true;
echo var_dump($a);
echo var_dump($b);
echo var_dump($c);
echo var_dump($d);
echo var_dump($e);
?>
The result is
The above is the official start of PHP learning (1) For more related content, please pay attention to the PHP Chinese website (www.php.cn)!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

查找方法:1、用strpos(),语法“strpos("字符串值","查找子串")+1”;2、用stripos(),语法“strpos("字符串值","查找子串")+1”。因为字符串是从0开始计数的,因此两个函数获取的位置需要进行加1处理。


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