Có 120+ tài liệu thuộc chủ đề "java"
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To then return the third element in the second row of this array, you would use the following PHP command, which will display an “x”:. It will return the contents of the matchbox three along and two down.. Variable names must start with a letter of the alphabet or the _ (underscore) character.. The variable $High_Score is not the same...
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PHP comes ready-made with dozens of predefined constants that you generally will be unlikely to use as a beginner to PHP. However, there are a few—known as the magic constants—that you will find useful. The names of the magic constants always have two underscores at the beginning and two at the end, so that you won’t accidentally try to name...
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In this chapter, you will get a thorough grounding in how PHP programming works in practice and how to control the flow of the program.. 9” (20 is greater than 9) is TRUE , and the expression “5. For each line, it prints out a letter between a and d , followed by a colon and the result of the...
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In the case of an if statement, you could imagine coming across a detour sign that you have to follow if a certain condition is TRUE . The contents of the if condition can be any valid PHP expression, including equality, comparison, tests for zero and NULL , and even the values returned by functions (either built-in functions or ones...
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Example 4-31 shows a modified version of the multiplication table for 12 code using such a loop.. Of course, if you have more than a single statement inside a do...while loop, remember to use curly braces, as in Example 4-32.. Example 4-33 shows how you could write the multiplication table program with a for loop.. Outputting the times table for...
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As you can see, the strrev function reversed the order of characters in the string, str_repeat repeated the string “Hip ” twice (as required by a second argument), and strtoupper converted “hooray!” to uppercase.. The first line of the syntax indicates that:. Function names are case-insensitive, so all of the following strings can refer to the print function: PRINT ,...
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The _r stands for “in human readable format.” In the case of the new object $object , it prints the following:. User Object ( [name] =>. Creating an Object. To create an object with a specified class, use the new keyword, like this: object = new Class . On the first line, we simply assign an object to the User...
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echo "[Class Dad] I am your Father<br />";. echo "[Class Son] I am Luke<br />";. If you wish to ensure that your code calls a method from the current class, you can use the self keyword, like this:. When you extend a class and declare your own constructor, you should be aware that PHP will not automatically call the constructor...
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A simple design feature in PHP’s array syntax makes it possible to create arrays of more than one dimension. echo "<pre>";. echo "</pre>";. To make things clearer now that the code is starting to grow, I’ve renamed some of the elements. Once the array data has been assigned, I use a pair of nested foreach...as loops to print out the...
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Not only can you specify a conversion type, you can also set the precision of the dis- played result. To ensure that such values are correctly stored internally, but displayed with only two digits of precision, you can insert the string “.2” between the % symbol and the conversion specifier:. printf("The result is: $%.2f . The result is $10.29. But...
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As with moving a file, a warning message will be displayed if the file doesn’t exist, which you can avoid by using file_exists to first check for its existence before calling unlink. Often you will want to add more data to a saved file, which you can do in many ways.. You can use one of the append write modes...
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But what’s the difference between the two markup languages?. As more and more devices such as iPhones and BlackBerries become web-enabled, it is increasingly important to ensure that web content looks good on them as well as on a computer’s web browser. This incorporates the contents from the HTML 4.01 standard but requires the use of XML syntax.. This version...
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But first you should type the following to log in to your MySQL system:. If you have a password, enter it. Once you are logged in, type the following to test the program—you should see some- thing like Figure 8-3 in response:. If this procedure fails at any point, please refer to the section “Installing a LAMP on Linux” on...
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They can both hold the same number of values—just picture a signed number as being shifted halfway to the left so that half its values are negative and half are positive. Data type Bytes used Minimum value (Signed/Unsigned) Maximum value (Signed/Unsigned). To specify whether a data type is signed or unsigned, use the UNSIGNED qualifier. The following example creates a...
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uses the UPDATE and WHERE keywords, which are explained in more detail in the upcoming section “Querying a MySQL Database” on page 183.. ALTER TABLE classics ADD PRIMARY KEY(isbn);. Once you have typed in these commands, the results should look like the screenshot in Figure 8-8. Note that the keywords PRIMARY KEY replace the keyword INDEX in the ALTER TABLE...
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ORDER BY. SELECT author,title FROM classics ORDER BY author;. As you can see, the first query returns the publications by author in ascending alpha- betical order (the default), and the second returns them by title in descending order.. If you wanted to sort all the rows by author and then by descending year of publication (to view the most recent...
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Chapter 8 provided you with a good grounding in the practice of using relational da- tabases with structured query language. It’s very important that you design a database correctly before you start to create it;. Sitting down with a sheet of paper and a pencil and writing down a selection of the queries that you think you and your users...
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In fact I would go so far as to say you should denormalize any commonly looked-up data as much as you can.. You see, if you have data duplicated across your tables, you can substantially reduce the number of additional requests that need to be made, because most of the data you want is available in each table. This means...
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The command in Example 9-8 stores the backup file into the current directory. You must also ensure that the directory you are backing up to has the right permissions set to allow the file to be written.. If you echo the backup file to screen or load it into a text editor, you will see that it comprises sequences of...
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So, replace the for loop of query.php (in Example 10-5) with the new loop in Example 10-6, and you will find that you get exactly the same result that was displayed in Figure 10-1.. Example 10-6. '<br />';. '<br /><br />';. In this modified code, only one-fifth of the calls are made to a MySQL-calling function (a full 80 percent...