我的字符串包含"$a==1||$b==2||$c==3"之类的条件。
如何使用IF语句评估此字符串（作为条件）？
答案 0 :(得分：1)
您可以使用Eval function来评估它，但首先，您需要连接一些代码：
$yourString = "$a==1||$b==2||$c==3";
$evalString = "if(".$yourString .")return true;";
$evaluation = eval($evalString);
在上面的这种情况下，如果任何条款为真，则返回true。
OBS：变量$ a，$ b，$ c应在执行前声明。
答案 1 :(得分：0)
要评估此条件，您可以使用eval（）。 例如：
2016-03-02 19:04:11.509 WARN 4476 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'newsService' defined in file [C:\Users\Lukasz\IdeaProjects\NewsSystem_REST\build\classes\main\com\newssystem\lab\dao\NewsService.class]: Unsatisfied dependency expressed through constructor argument with index 0 of type [com.newssystem.lab.dao.NewsDao]: : No qualifying bean of type [com.newssystem.lab.dao.NewsDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.newssystem.lab.dao.NewsDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
2016-03-02 19:04:11.516 INFO 4476 --- [ main] o.apache.catalina.core.StandardService : Stopping service Tomcat
2016-03-02 19:04:11.538 ERROR 4476 --- [ main] o.s.boot.SpringApplication : Application startup failed
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'newsService' defined in file [C:\Users\Lukasz\IdeaProjects\NewsSystem_REST\build\classes\main\com\newssystem\lab\dao\NewsService.class]: Unsatisfied dependency expressed through constructor argument with index 0 of type [com.newssystem.lab.dao.NewsDao]: : No qualifying bean of type [com.newssystem.lab.dao.NewsDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.newssystem.lab.dao.NewsDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:749) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:185) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1143) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1046) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:510) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839) ~[spring-context-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538) ~[spring-context-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118) ~[spring-boot-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:766) [spring-boot-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.boot.SpringApplication.createAndRefreshContext(SpringApplication.java:361) [spring-boot-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:307) [spring-boot-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1191) [spring-boot-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1180) [spring-boot-1.3.2.RELEASE.jar:1.3.2.RELEASE]
at com.newssystem.lab.NewsSystemApplication.main(NewsSystemApplication.java:24) [main/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_25]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_25]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_25]
at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_25]
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) [idea_rt.jar:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.newssystem.lab.dao.NewsDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1373) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1119) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:813) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:741) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]
... 24 common frames omitted
你要小心使用eval（）。我不建议使用它，除非你真的必须和你确信$条件不是任何人都可以篡改的。
答案 2 :(得分：0)
简单易行。试试这个
<?php
$a="yes";
$b="ok";
$c="yes";
if(($a=='yes') || ($b=='ok') || ($c=='yes')){
echo "If a=yes or b=ok or c=yes you got this";
} else {
echo "You got this, because a!=yes or b!=ok or c!=yes";
}
?>
答案 3 :(得分：0)
而不是使用eval() - 在你的上下文中可能只是将表达式限制为你想要/应该允许的内容的噩梦 - 你可以创建一个只能处理那些操作的解析器/词法分析器你想要的。
你可以，例如看一下梨包PHP_LexerGenerator和PHP_ParserGenerator。或者搜索stackoverflow以获取有关[php] parser的答案。
只是为了好玩：
PHP 7 introduced编译过程中的Abstract Syntax Tree层
https://github.com/nikic/php-ast处的扩展将此AST层暴露给userland脚本。使用这个[a]限于php7 +，b）不清楚这个扩展是否会在将来维护，我只是通过谷歌找到它你可以设置一个解释器，例如。
<?php
$data = [
['a'=>5, 'b'=>6, 'c'=>7],
['a'=>5, 'b'=>6, 'c'=>3],
['a'=>5, 'b'=>2, 'c'=>7],
['a'=>1, 'b'=>6, 'c'=>7],
['a'=>1, 'b'=>2, 'c'=>7],
['a'=>7, 'b'=>2, 'c'=>3],
];
$expressions = [
'$a==1||$b==2||$c==3',
'($a==1&&$b==2)||$c==3',
'$a==1&&($b==2||$c==3)'
];
foreach( $expressions as $x ) {
$ep = new ExpressionParser($x);
echo $x, "\r\n";
foreach( $data as $scope ) {
$result = $ep->eval( $scope );
printf(
" %s => %s\r\n",
compact_var_export($scope),
compact_var_export($result)
);
}
}
class ExpressionParser {
public function __construct($expr) {
$ast = ast\parse_code('<?php '.$expr.';', $version=20);
if (!$ast || ast\AST_STMT_LIST!=$ast->kind ) {
throw new InvalidArgumentException('unable to parse expression');
}
else if ( 1!==count($ast->children) || ast\AST_BINARY_OP!==$ast->children[0]->kind ) {
throw new InvalidArgumentException('only one binary expression allowed');
}
else {
$this->ast = $ast->children[0];
}
}
public function eval($scope) {
return evalOp($scope, $this->ast);
}
}
function evalOp($scope, $ast) {
static $handler = null;
if ( is_null($handler) ) {
$handler = [
ast\AST_UNARY_OP => [
ast\flags\UNARY_BOOL_NOT => function($scope, $c) { return !evalOp($scope, $c[0]); },
ast\flags\UNARY_BITWISE_NOT => function($scope, $c) { return ~evalOp($scope, $c[0]); },
ast\flags\UNARY_MINUS => function($scope, $c) { return -evalOp($scope, $c[0]); },
],
ast\AST_BINARY_OP => [
ast\flags\BINARY_BOOL_AND => function($scope, $c) { return evalOp($scope, $c[0]) && evalOp($scope, $c[1]); },
ast\flags\BINARY_BOOL_OR => function($scope, $c) { return evalOp($scope, $c[0]) || evalOp($scope, $c[1]); },
ast\flags\BINARY_BOOL_XOR => function($scope, $c) { return evalOp($scope, $c[0]) ^ evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_IDENTICAL => function($scope, $c) { return evalOp($scope, $c[0]) === evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_NOT_IDENTICAL => function($scope, $c) { return evalOp($scope, $c[0]) !== evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_EQUAL => function($scope, $c) { return evalOp($scope, $c[0]) == evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_NOT_EQUAL => function($scope, $c) { return evalOp($scope, $c[0]) != evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_SMALLER => function($scope, $c) { return evalOp($scope, $c[0]) < evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_SMALLER_OR_EQUAL => function($scope, $c) { return evalOp($scope, $c[0]) <= evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_GREATER => function($scope, $c) { return evalOp($scope, $c[0]) > evalOp($scope, $c[1]); },
ast\flags\BINARY_IS_GREATER_OR_EQUAL => function($scope, $c) { return evalOp($scope, $c[0]) >= evalOp($scope, $c[1]); },
],
ast\AST_VAR => function($scope, $a) {
if ( !isset($scope[$a->children[0]]) ) {
throw new InvalidArgumentException('undefined variable: '.$a->children[0]);
}
else {
return $scope[$a->children[0]];
}
}
];
}
if ( !is_object($ast) ) {
return $ast;
}
else if ( !isset($handler[$ast->kind]) ) {
throw new InvalidArgumentException('unsupported operation type');
}
else if ( is_array($handler[$ast->kind]) ) {
if ( !isset($handler[$ast->kind][$ast->flags]) ) {
throw new InvalidArgumentException('unsupported operation');
}
else {
return $handler[$ast->kind][$ast->flags]($scope, $ast->children);
}
}
else {
return $handler[$ast->kind]($scope, $ast);
}
}
function compact_var_export($x) {
return preg_replace('!\s+!m', ' ', var_export($x, true));
}
输出
$a==1||$b==2||$c==3
array ( 'a' => 5, 'b' => 6, 'c' => 7, ) => false
array ( 'a' => 5, 'b' => 6, 'c' => 3, ) => true
array ( 'a' => 5, 'b' => 2, 'c' => 7, ) => true
array ( 'a' => 1, 'b' => 6, 'c' => 7, ) => true
array ( 'a' => 1, 'b' => 2, 'c' => 7, ) => true
array ( 'a' => 7, 'b' => 2, 'c' => 3, ) => true
($a==1&&$b==2)||$c==3
array ( 'a' => 5, 'b' => 6, 'c' => 7, ) => false
array ( 'a' => 5, 'b' => 6, 'c' => 3, ) => true
array ( 'a' => 5, 'b' => 2, 'c' => 7, ) => false
array ( 'a' => 1, 'b' => 6, 'c' => 7, ) => false
array ( 'a' => 1, 'b' => 2, 'c' => 7, ) => true
array ( 'a' => 7, 'b' => 2, 'c' => 3, ) => true
$a==1&&($b==2||$c==3)
array ( 'a' => 5, 'b' => 6, 'c' => 7, ) => false
array ( 'a' => 5, 'b' => 6, 'c' => 3, ) => false
array ( 'a' => 5, 'b' => 2, 'c' => 7, ) => false
array ( 'a' => 1, 'b' => 6, 'c' => 7, ) => false
array ( 'a' => 1, 'b' => 2, 'c' => 7, ) => true
array ( 'a' => 7, 'b' => 2, 'c' => 3, ) => false
（我并不擅长这个。因此，专家可能会发现这个笨拙，有缺陷甚至是错误的;随意评论;-)）